System on a chip (SoC) devices are becoming more prevalent. SoCs incorporate a large amount of processing functionality with (typically) heterogeneous devices on a single semiconductor device, avoiding the need for multiple components. As SoCs become more complicated over time, it becomes more important to have a common backbone for modular design and integration. At the same time, as the number of devices and subsystems grow, efficient and low overhead power management becomes more difficult as the number of subsystems expands. This is so, as the heterogeneous subsystems can have different frequency and voltage requirements. Further, each heterogeneous resource typically has its own power management (PM) protocol, generally developed on an ad hoc basis and lacking any standard signaling mechanisms.